1. Field of the Invention
This invention relates in general to vehicular collision avoidance systems and in particular to an easily retrofittable, collision warning apparatus for vehicles that alerts the operator to potential obstacles in the vicinity of the vehicle during operations such as parking and driving in stop and go traffic conditions.
2. Description of Related Art
Traffic statistics show that every 1.6 minutes, a driver backs up into trouble with their car. Children and animals are at risk constantly. Restricted operator visibility in front of the vehicle is a problem for school buses. Young children darting into an obscured area of the bus unseen by the operator have contributed to fatalities. A major cause of vehicle accidents today involves front-to rear collisions, particularly in stop and go traffic. Insufficient room between vehicles is the primary cause of rear end collisions. Most vehicles have one or more blind spots surrounding the vehicle which cannot be easily observed by the motorist. These blind spots are usually located at the rear corners of the vehicle due to obstructions that block a full view. This is particularly apparent when the vehicle is being reversed, in which case, lack of full view may cause collisions resulting in loss of life and property. In another instance, when a motorist is pulling into or backing out of a parking space, it is difficult for the motorist to maintain attention simultaneously on all sides of the vehicle in order to avoid hitting adjacent objects such as other cars. Not only do such accidents result in loss of life and injuries, but drive up the cost of automobile insurance and repairs. These types of incidents account for the majority of accidents involving vehicles and have spurred the development of collision warning systems.
Parking a vehicle accurately within a garage requires accurate positioning to prevent contact with the front wall and objects placed along the wall, while providing sufficient clearance behind the vehicle. The detection of objects around a vehicle is an ever-growing concern, especially with the increased popularity of the larger vehicles such as minivans, trucks, and RVs.
The simplest collision warning systems are passive. They comprise a system of mirrors, markers, and feelers installed around the periphery of the vehicle. These give the operator a visual indication of the extremities of the vehicle so that the operator can estimate the spatial separation between the vehicle and nearby obstacles. Such techniques have limited utility since they rely on the visual acuity and depth perception of the individual, and are ineffective in poor lighting conditions. Luxury car makers have begun to offer active parking aids as standard equipment on their higher end models. An example is the Parktronics system from Mercedes Benz. These systems utilize a plurality of distance measuring sensors mounted around the periphery of the vehicle in the vicinity of the vehicle fenders. The distance measuring sensors are connected to a display and warning system mounted in the vehicle dashboard that provides a continuous indication of potential obstacles in the vehicle""s path during operations such as parking. Such is the usefulness and urgency for such a collision warning system that it is expected to be standard equipment on all new cars by the end of the decade. Since the typical life span of the average car in the US is well over a decade, it will be a long time before all the vehicles are equipped with collision warning systems. Thus, there is an urgent need for a collision warning system that is easily retrofittable to existing vehicles for them to remain compliant with evolving safety standards for vehicles.
To address this need, Topix has recently introduced the Mini II car reversing aid that comprises a distance indicator unit mounted within the passenger cabin, and a plurality of distance measuring sensors that are connected to the rear bumper. The distance indicator unit provides a readout of the distance and/or an audio signal indicative of distance to an object. Similar systems are available in kit form such as the K3502 parking radar from Velleman Kits. For all these systems, the distance measuring sensor has to be electrically connected to the electrical system of the vehicle as well as to an indicator unit mounted within the passenger compartment. Electrical wiring that is preferably concealed has to be installed between the indicator unit and the distance measuring sensors.
Several embodiments of collision warning and avoidance systems have been described in the prior art. Schofield U.S. Pat. No. 5,786,772 describes a passive mirror based system. Sindle U.S. Pat. No. 3,842,397 describes an ultrasonic distance detector for vehicles using a plurality of transducers located around the sides of the vehicle and connected to transmitters for sending sonic pulses to distant objects. Each of the transducers is connected to a receiver for detecting sonic echoes from close objects. The output of each receiver is connected to individual indicator lamps and a warning device such as a horn so that if any of the lamps are energized, the driver is warned that one side of the vehicle is in danger of a collision. The warning is activated if the obstacles are within a predetermined distance that is set based on the speed of the vehicle.
A variety of distance measuring sensors employing ultrasonic, radio frequency, microwave, optical, and video techniques for distance sensing have been described. These sensors determine the proximity of different sides of a vehicle with respect to external objects. For short distance sensing applications (i.e. sensing distances under 10 feet), ultrasonic sensing is the preferred method. Various embodiments and refinements using ultrasonic sensors for collision warning systems have been described in Sindle U.S. Pat. No. 3,842,397, Sindle U.S. Pat. No. 4,015,232, Duncan U.S. Pat. No. 4,240,152, Vancha U.S. Pat. No. 4,326,273, Kodera U.S. Pat. No. 4,404,541, Kodera U.S. Pat. No. 4,442,512, Tsuda U.S. Pat. No. 4,490,716, Gelhard U.S. Pat. No. 4,500,977, Bruggen U.S. Pat. No. 4,561,064, Tsuji U.S. Pat. No. 4,658,385, Miller U.S. Pat. No. 4,694,295, Riedel U.S. Pat. No. 4,910,512, Forster U.S. Pat. No. 4,980,869, Friberg U.S. Pat. No. 5,208,586, Truesdell U.S. Pat. No. 5,229,975, Oualiwa U.S. Pat. No. 5,235,316, Gauthier U.S. Pat. No. 5,303,205, Park U.S. Pat. No. 5,483,501, Waffler U.S. Pat. No. 5,726,647, and Akuzawa U.S. Pat. No. 5,546,086. Similar devices are also described in Park U.S. Pat. No. 5,483,501 and Toda U.S. Pat. No. 5,515,341.
Other distance sensing means that have been described include capacitive (Stahovec U.S. Pat. No. 4,300,116), light based (Endo U.S. Pat. No. 4,383,238), radar (Manor U.S. Pat. No. 4,700,191, Pakett U.S. Pat. No. 5,517,196, and Henderson U.S. Pat. No. 5,670,962), doppler radar (Dombrowski U.S. Pat. No. 4,797,673 and Gallagher U.S. Pat. No. 5,453,740), optical imaging (Dye U.S. Pat. No. 4,872,051, Bottesch U.S. Pat. No. 5,166,681, and Truesdell U.S. Pat. No. 5,229,975), electro-optic (Taylor U.S. Pat. No. 5,249,157), infrared (Suds U.S. Pat. No. 5,463,384), laser radar (Straw U.S. Pat. No. 5,529,138), radiant energy (Cho U.S. Pat. No. 5,646,613), video imaging (Abersfelder U.S. Pat. No. 5,646,614), electromagnetic radiation (Signore U.S. Pat. No. 5,682,136), articulated reflector (Richardson U.S. Pat. No. 5,714,947), and MMIC (Agravante U.S. Pat. No. 5,767,793).
Radar and doppler radar systems are best suited for long range sensing and do not provide sufficient accuracy for objects closer than ten feet. In addition, they are expensive, lack signal directionality, and need regular maintenance and calibration. Infrared detectors are prone to errors caused by temperature fluctuations. Reflections from nearby objects or reflective surfaces reduce the sensitivity of the infrared sensors. The viewing angle of these systems is limited. Light transmissions are obscured by dust, snow, rain or other environmental factors. To circumvent the limitations of a single sensor technology, multiple sensing techniques may be combined as described by Yoshioka U.S. Pat. No. 5,479,173, Shaffer U.S. Pat. No. 5,612,883, and Nashif U.S. Pat. No. 5,754,123.
Reliability, insensitivity to environmental conditions, and robustness in hostile environments are some of the other key requirements. Ultrasonic sensing is the preferred technique based on these factors. The short-range constraint for ultrasonic sensing makes them unsuitable for vehicles traveling over 5-10 miles per hour.
In addition to distance, the warning can also be generated based on speed, direction and the likelihood of the vehicle hitting the obstacles as has been described in Chey U.S. Pat. No. 4,626,850, Shyu U.S. Pat. No. 5,091,726, Shaw U.S. Pat. No. 5,314,037, Katiraie U.S. Pat. No. 5,347,273, Waffler U.S. Pat. No. 5,477,461, Gaus U.S. Pat. No. 5,572,484, Yoshioka U.S. Pat. No. 5,585,798, Arai U.S. Pat. No. 5,680,117, Gilon U.S. Pat. No. 5,684,474, Kikuchi U.S. Pat. No. 5,731,779, Smithline U.S. Pat. No. 5,734,336, Shirai U.S. Pat. No. 5,751,211, Harron U.S. Pat. No. 5,764,136 and Minissale U.S. Pat. No. 5,777,563.
The warning may be communicated by means of a display within the cabin (Lee U.S. Pat. No. 4,943,796 and Blank U.S. Pat. No. 5,708,410), lights on the outside of the vehicle to alert other drivers (Caine U.S. Pat. No. 4,600,913), external speakers to alert other drivers (Sindle U.S. Pat. No. 5,173,881), audible signals emanating from various zones of the car (Takeuichi U.S. Pat. No. 4,528,563), audible tones of varying frequency (Hollowbush U.S. Pat. No. 5,059,946 and Abst U.S. Pat. No. 5,339,075) and inter-vehicle communication (Huskier U.S. Pat. No. 5,068,654).
Collision warning systems have evolved to collision avoidance systems in which the trajectory of the vehicle is automatically or manually altered in order to avoid collisions. The warning signals may be used to calculate safe stopping parameters (Emry U.S. Pat. No. 5,436,835) and used to take corrective action such as guiding the driver to take evasive action (Shyu U.S. Pat. No. 4,931,930), assisting the driver during parking (Hoetzel U.S. Pat. No. 5,587,938, Czekaj U.S. Pat. No. 5,742,141), and automatically engaging the vehicles control system to prevent collision (Dombrwski U.S. Pat. No. 4,803,488, David U.S. Pat. No. 4,833,469, Dombrowski U.S. Pat. No. 4,864,298, Reppas U.S. Pat. No. 5,598,164, and Katoh U.S. Pat. No. 5,748,477).
Adams U.S. Pat. No. 5,528,217 describes retrofitting vehicles with collision warning systems using the existing electrical systems. Vehicles pre-wired during manufacture with wiring harnesses used to operate and monitor such vehicle functions as, side and back marker lights, license plate lamps, turn signal and hazard lamps, stop lamps, back-up lights and anti-lock brake devices can be retrofitted. However, since this method involves modification of the original equipment wiring, it may void manufacturer warranty unless performed by an accredited professional.
The requirement for professional or factory installation for prior art systems, involves considerable inconvenience and expense, and is the singular drawback that has slowed their widespread acceptance as retrofits to existing vehicles. An important requirement for ease of retrofit is the elimination of cables between the distance sensors and the display unit as well as cables to each of these units to provide electrical power. Use of wireless communication between the display and the distance sensors (Smithline U.S. Pat. No. 5,734,336) eliminates the set of wires required for communication. Wireless communication with external devices for vehicles is well known. For example keyless car entry, remote garage door openers, and remote car alarms are in widespread use. Schofield U.S. Pat. No. 5,798,688 describes installation of an electromagnetic communication circuit on a rear view mirror assembly, the communication circuit being used to communicate with external devices such as keyless entry systems and garage door openers. Various modes of communication have been disclosed in vehicle collision avoidance systems. The communication may use infrared means, RF means (Smithline U.S. Pat. No. 5,734,336), microwave means (Lemelson U.S. Pat. No. 5,983,161), and ultrasonic means (Kayo U.S. Pat. No. 4,580,250).
Incorporation of an on-board battery that is preferably rechargeable eliminates the need for external wiring. Pena U.S. Pat. No. 5,801,646 describes a traffic alert system in which a ground mounted strobe has a backup battery that is recharged using a solar panel. Unfortunately, solar panels are not well-suited for vehicular applications, especially when they are to be mounted on the vehicle exterior. Solar panels are fragile and are susceptible to damage. Any dust that settles on the solar panel drastically decreases its power generation capability. Most importantly, they are relatively expensive and require a large surface area to generate sufficient power for a retrofittable collision avoidance system.
Implementation of wireless communication and an on-board battery for the remote units is the first step in achieving an easily retrofittable collision avoidance system. However, additional improvements are desirable for a commercially viable device. Since ease of retrofittability has not been a primary concern of the prior art, these improvements have not been anticipated or applied in the prior art. For retrofittable collision avoidance systems, means must be developed to conserve on-board battery power to achieve a long battery life. This is essential since a battery charging source such as the solar panel described by Pena (U.S. Pat. No. 5,801,646) is impractical. Customers demand battery life exceeding several months for ease of maintainability. In addition, the on-board battery must be very compact so that a small size can be achieved for the distance measuring sensors and the display unit. Ideally the distance measuring sensors and the display units must be smaller than 4xe2x80x3xc3x971xe2x80x3xc3x971xe2x80x3 so that they are aesthetically pleasing and can be easily mounted to the vehicle bumper or license plate and vehicle dashboard respectively. Recently compact, xc2xdAA sized batteries operating at 3.6 V with rated capacity of 1 Ah have become available. These batteries are ideally suited from the size viewpoint, but their output voltage is too low to power traditional collision warning systems. These systems have been designed to operate from vehicle power which ranges from 12 V-24 V.
To achieve a retrofittable device for the consumer market, several improvements must be made to the collision avoidance system proposed by Smithline (U.S. Pat. No. 5,734,336). These include the ability to operate for extended periods from compact, low voltage battery sources and ease of system expandability from a single sensor to a plurality of sensors. Incorporation of these improvements will enable a compact, easily expandable retrofittable collision avoidance system.
Power consumption can be reduced by employing power management such as has been described in pending application Ser. No. 09/159,137. This prior application provides for an unswitched and switched power supply to selectively supply power to various circuits to turn them on as needed with the objective of lowering the power consumption. The circuits are turned off when not in use. Thus power consumption is reduced several fold. Another desirable feature is to activate the remote units based on a wireless wakeup command from the base unit to further reduce power consumption. This application describes additional improvements to the embodiments described in the prior application to enable operation from a compact, low voltage battery source and achieve a long battery life. Consumers would not like to replace the battery more frequently than once every few months. In the prior application a conventional RF receiver that was powered by the unswitched power means was used. Power consumption by such wireless receivers is in the mW range, which would translate to approximately 1 month of battery life for a compact, low voltage battery. Thus a lower power consumption by the receiver is required if a battery life of several months is to be achieved.
To achieve more effective power conservation, an advanced receiver that has programmable sleep and active modes replaces the conventional receiver in the remote units. A conventional receiver can be upgraded by combining it with a microcontroller that supports a sleep mode. Such a receiver or a receiver/microcontroller combination switches from an ultra-low power sleep mode to a higher power active mode for a brief duration (for e.g. 5-20 ms) periodically (e.g. every 1-3 s) to listen for a wakeup signal from the base station. The duration of the sleep and active modes is normally programmable so that it can be optimized for a specific application. If no wakeup signal is detected, the wireless receiver returns to its lowest power sleep mode. When a wakeup signal is detected, the receiver switches to the active mode and signals the switched power means to selectively supply power to the various circuits in the remote units. This mode of operation reduces power consumption in the remote units to the microwatt level when the colision warning system is idle. A similar receiver may be used in the base unit as well to lower power consumption. Most receivers of this type are packaged as transceivers that can transmit as well as receive signals. Thus more elaborate signaling techniques between the transceivers in the base and remote units can be devised.
The collision warning system remains mostly in the idle state unless activated by the user. Typically, the user might activate the system for periods ranging from a few minutes to a couple of hours each day. Thus lowering power consumption in the idle mode is vital to increasing the battery life. This additional power conservation is necessary in order to achieve the desired battery life of over three months. The circuit topology for realizing this enhanced mode of power conservation has not been anticipated or applied to collision warning or traffic alert systems.
Several circuit elements in the collision warning system require operating voltages exceeding 9 V and often as high as 15 V-30 V. For example, ultrasonic transducers used for distance sensing require drive voltages of 12 V-30 V. This conflicts with the desire to use a compact, low voltage on-board battery. Even with the most efficient battery technology such as a lithium battery, the highest voltage from a single battery is 3.6 V, which is more than twice the voltage delivered by a conventional alkaline battery. Stacking multiple batteries in series to achieve the desired voltage while feasible is impractical because of size and cost constraints. If smaller batteries are stacked in series to boost the voltage, the battery capacity is compromised assuming that the total battery size remains unchanged. A more practical approach is to employ voltage booster circuits for powering circuits that need higher voltages. These voltage boosters are capable of generating output voltages of 6 V-30 V using low input starting voltages (e.g. 1 V-5 V). Voltage boosters have not been described in the prior art on collision warning systems.
A retrofittable system must also be easily expandable so that the user can easily add or remove distance measuring sensors from the system with minimum effort. An auto configuration capability in which the system automatically detects its configuration and adjusts its operation accordingly is desirable. Once again, this feature has not been anticipated or applied to existing collision warning systems.
The object of the present invention is to improve upon the collision warning system described in Ser. No. 09/159,137 with the aforementioned features so that an easily expandable, compact, collision warning apparatus can be installed quickly and easily by the average vehicle operator, without compromising performance and functionality. The principal elements of this invention are the subject of this application.
The object of the present invention is to provide a retrofittable collision warning apparatus for vehicles that when enabled by the operator, senses the distance between the vehicle and obstacles in the vicinity, and communicates the information to the operator through audio and/or visual means. A vehicle collision warning apparatus that warns an operator of obstacles in the vicinity of the vehicle, in accordance with the present invention, comprises: a base unit means located within a cabin of said vehicle that accepts said operator commands, controls operation of said collision warning apparatus, and communicates said obstacle position information to said operator; and a remote unit means located around the periphery of said vehicle that respond to inputs from said base unit means, measures the distance between said vehicle and said obstacles in the proximity, and communicates said obstacle position information to said base unit means through wireless means, and wherein the remote unit means includes an unswitched power means that supplies power to a receiving means for receiving wireless signals from said base unit means and a switched power means for supplying power to additional circuits within said remote unit means based on a wireless transmission from said base unit.